1. Field of the Invention
The present invention relates to stator cores of the type having laminated end shields provided with radially-extending ventilation passages.
2. Prior Art
In various types of rotating machines, for example large turbine generators, each axial end of the stator core is provided with laminated end shields and these end shields must be formed to present radial ventilation passages for the flow of cooling air during generator operation.
Each end shield is composed of a plurality of thin plates, or laminations, and the conventional manner of forming ventilation passages is to secure generally radially extending vent fingers to one or more of these laminations. The vent fingers are attached to an associated lamination by a mechanical riveting connection. Typically, the lamination, or vent plate, is provided with a plurality of square openings and each end finger is provided with mating projections which extend through respective openings after which each projection is deformed, as by hammering, to, in effect, rivet each end finger to the associated vent plate.
Arrangements of this type present certain inherent drawbacks. For example, because of the manufacturing limitations, the size, and particularly the cross section, of each vent finger must be kept relatively small. However, vent fingers having a small cross section have a limited ability to resist the high clamping forces applied to hold the stator laminations and the end shield laminations together in a secure manner. It can occur that the requisite clamping forces will result in crushing of the vent fingers, particularly since all of the clamping forces must be transmitted by the vent fingers. Because of this localized compressive loading, the laminated end shield tends to flare, resulting in loosening of the laminations.
While each vent finger may be attached by spot welding, mechanical riveting of the type described above is generally preferred.